America’s iodised-salt safety net is fraying as diets change

A voluntary fortification programme that helped eliminate goitre is losing reach, leaving pregnant women and developing babies increasingly vulnerable to iodine deficiency.

Iodised salt, once a simple public health triumph in the United States, is showing signs of strain as diets change and more people reach for non-iodised alternatives. That matters because iodine is essential for thyroid hormones, which support brain development in the womb and in early childhood, and remain important throughout life. In recent years, researchers have found that a substantial share of Americans are not getting enough iodine, with pregnant women especially vulnerable to falling short.

The shift is striking because the country once turned a severe deficiency problem into a major success story. According to historical accounts and medical reviews, iodine deficiency was widespread in the early 20th century, especially across inland northern regions where soil and water contained little of the nutrient. The resulting enlargement of the thyroid gland, known as a goitre, was so common in parts of the Midwest, Appalachians and the Pacific Northwest that those areas became known as the “goitre belt”. Michigan medical leaders and salt producers helped popularise iodised table salt in the 1920s, and the practice spread nationally.

That intervention changed public health. By the middle of the century, goitres had become far less common, and later research linked improved iodine intake to better educational and cognitive outcomes. Historians and nutrition researchers have described the campaign as one of the clearest examples of a cheap, population-wide fortification effort preventing disease before it starts. UNICEF has also long warned that iodine deficiency remains a major global cause of preventable brain injury in newborns, underlining that the problem never disappeared worldwide.

Yet the United States may be losing ground. A study published in the Journal of Nutrition found that iodine deficiency roughly doubled between 2001-02 and 2017-18, with nearly half of pregnant women falling short of recommended intake. The Centers for Disease Control and Prevention said in its 2026 nutrition report that women of reproductive age were hovering on the edge of mild iodine deficiency. Elizabeth Pearce, an endocrinologist at Boston University, has warned that even modest shortages during pregnancy may be associated with lower IQ in children.

Several modern eating patterns appear to be weakening the safety net. More than half of table salt sold in US stores is now non-iodised, according to one analysis, while much of the salt Americans consume comes from processed and packaged foods that usually use non-iodised varieties. Milk can be a source of iodine, but its levels vary, and people who avoid dairy may be at greater risk. The recommended intake for adults is 150 micrograms a day, rising to 220 micrograms in pregnancy and 290 micrograms while breastfeeding. Because the first trimester is a critical period for brain development, major medical groups advise pregnant people, those who are breastfeeding and those trying to conceive to take a daily iodine supplement.

The wider lesson is that fortification only works when it is used consistently. Many countries now require salt iodisation, but the United States relies on voluntary use, which worked well for decades because home cooking was common and iodised salt was widely used. As diets have shifted, that protection has become patchier. Public health specialists say the answer is not more salt overall, but making sure that the salt people do use is iodised and that pregnant people get enough iodine from supplements or food. Without that, a preventable nutritional gap could again affect the next generation.